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Maharashtra State BoardSSC (English Medium) 9th Standard

Prove that, if the bisector of ∠BAC of ΔABC is perpendicular to side BC, then ΔABC is an isosceles triangle. - Geometry

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Question

Prove that, if the bisector of ∠BAC of ΔABC is perpendicular to side BC, then ΔABC is an isosceles triangle.

Sum

Solution

Given: Seg AD is the bisector of ∠BAC. Seg AD ⊥ seg BC.

To prove: ΔABC is an isosceles triangle.

Proof:

In ∆ABD and ∆ACD,

∠BAD ≅ ∠CAD     ...[seg AD is the bisector of ∠BAC]

seg AD ≅ seg AD     ...[Common side]

∠ADB ≅ ∠ADC     ...[Each angle is of measure 90°]

∴ ∆ABD ≅ ∆ACD    ...[ASA test]

∴ seg AB ≅ seg AC    ...[c. s. c. t.]

∴ ∆ABC is an isosceles triangle.

shaalaa.com
Angle Bisector Theorem
  Is there an error in this question or solution?
Chapter 3: Triangles - Practice Set 3.4 [Page 44]

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